Sahel Precipitation Index

Sahel Precipitation Index (20-10N, 20W-10E), 1900 - May 2015

Notice: The digital monthly values of the index are through May 2015, and further updates are not planned. Several factors are contributing to this:
i) updates of this index are not funded
ii) NOAA NCDC has decided to not to update the gridded precipitation data set that is used. Other data sets could be used, and that will require comparisons with the present product.
iii) Matlab has changed the way they write PostScript files, and figuring out how to fix or get around this will take time.
Please send me references for research you have published using this index ( mitchell@atmos.washington.edu ).

analyses | digital values | applications

Important! Please use the digital object identifier doi:10.6069/H5MW2F2Q in your citation of this index.

Big GIF | PDF | PNG | PS
Data as a 2-column table (year, value in cm/month).
The anomalies are with respect to 1900-2013.

The Sahel rainy season is centered on June through October, and the means are taken for those months. An earlier version of this WWW page provides documentation on the Sahel precipitation climatology and year to year variability. Maps of the climatological African rainfall are also available. Sahel precipitation was above the long-term mean from 1915 through the late 1930s and during the 1950s-1960s, after which it was persistently below the longterm mean, with the largest negative anomalies in the early 1980s.

Big GIF | PDF | PNG | PS
The anomalies are with respect to 1950-2013 in this figure.

The averages are taken of NOAA Global Historical Climatology Network gridded rain gauge precipitation anomalies. The data for the Sahel in this data set are "raw precipitation stations," and have not undergone any "homogeneity adjustments" (more information). The averaging region was chosen from a rotated principal component analysis of African precipitation by Janowiak (1988).

An analysis of sampling in several formats: Big GIF | PDF | PNG | PS

Last month's precipitation anomaly in millimeters
(The month and year are identified in the lower left corner)

Climate Anomaly Monitoring System (CAMS) Outgoing Longwave Radiation Precipitation Index (OPI) data analyzed by the International Research Institute for Climate and Society (IRI).

References:
Janowiak, J. E., 1988: An investigation of interannual rainfall variability in Africa. J. Climate, 1, 240-255.

The Sahel precipitation index has a digital object identifier: doi:10.6069/H5MW2F2Q

The Sahel precipitation index has been used in the following publications:

Frost, L., Mace, D., P. Wraight, and L. Lewis, 2016: Edexcel A Level Y2 Geography Student Book, 978-1-2921-3964-7.

Haywood, J. M., A. Jones, N. Bellouin, and D. Stephenson, 2013: Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall. Nature Clim. Change, doi:10.1038/NCLIMATE1857.

Gray, Nick, 2015: Facing up to global warming. Springer Sci. Bus. Media, 406 pp, doi: 10.1007/978-3-319-20146-7

Hesse, C., Anderson, S., Cotula, L., Skinner, J. and Toulmin, C. 2013. Managing the Boom and Bust: Supporting climate resilient livelihoods in the Sahel. IIED Issue Paper. IIED, London

Sitch, S. and Drake, F. (2013) The changing water cycle. In Holden, J. (ed) Water Resources: an integrated approach. Routledge.

Revise Edexcel GCSE (9-1) Geography A Revision Workbook, 2017, ISBN 978-1-2921-3373-7.

Digital values:

The precipitation index is provided here in several formats. The anomalies are with respect to 1950-79.

A 3-column table: year, month, index value (cm).

A 1-column table, with only the index values (cm).

A table organized by years and months, with units of 0.1 mm.

Averages are in 0.1 mm, so "-917" is -9.17 cm precipitation anomaly with respect to 1950-79.

       jan  feb  mar  apr  may  jun  jul  aug  sep  oct  nov  dec
 1900   -6    7   -6  -10   98  200  514 -917 -185 -275  -43  -15
 1901   -8   -7   -6   10   68   78  378  229 -280 -201  -39  -15
 1902   -5   -8    4   -9 -116 -147  -15 -378 -729  -52  -40  -14
 1903   -7   -8  -12    6  187   36 -353 1066 -870 -298  -37  -16
 1904   -7   -8  -16  -27   98  203  -40  114 -642 -188   18   28
 1905   -3   11   -1  -34  -93  295   64  179   18  257  -32    8
 1906   -6    2  -36   51  103  153  708  829 -171  -31    7  191
 1907   -4   -5  -12  -73 -114  -14 -505 -206  -92 -116  -25  -15
 1908   -7  -15   15  -32 -120  -65  -77  450  -74 -230  -19   11
 1909    3   -4    2  144   60  213  131  488   28  -93  -33   -3
 1910   -7  -10  -44  -21  -70  -72  222   76  -79 -239  -45  -17
 1911   -8  -14   21  101  212  -78 -199 -182 -296 -183    4   -9
 1912    0  -12  -45   29 -169  -31 -359  257  -45 -151  -14    4
 1913   14  -12  -40  -25  -65 -152 -414 -329 -453 -203  -32   -2
 1914   -7  -12  -34  -66 -152  -19 -193   57  -46  -64   41  -12
 1915   -6  -10   34  140  107   96  -40  -37 -541 -150  -35  -11
 1916   -6   -8    4   95 -113 -118  -15  237  152 -280  -16  -10
 1917    0   -1  -26  -40  235 -338 -178  234  278 -338  -13   -8
 1918   -3  -10  -13  -10  137  394  117  298  115   -7  -40  -13
 1919   -6   -9  -15  -35  131 -130   94 -364 -100 -124  -30  -13
 1920   -3    6  -25  -10    2  101 -273  434   40 -237  -29  -14
 1921   -6   -7    1  -11   16 -134 -314   81 -163 -165   31  -10
 1922    1   -8  -17   60  -61 -168  -16  117  384  149   29   -6
 1923   16   -8    3   82  -86  -93   12  133 -108   30   24   -4
 1924   19   30   -3  -13  -90  239  255   77  284 -138   14   -9
 1925   -1  -10   20  -30    3    6 -154   57   12  163   -9  -12
 1926   -6   -9  -12  -43  -15  220  -53 -272 -282 -208    3  -10
 1927   -6   -2  -33   25  117  173 -127  742  116  214   30   -6
 1928   -1  -10    4   33  -13  -47 -136  617 -183  102  -33  -10
 1929   -6   -8   14  -17   76  279  -48  414    4  -46  -41   -3
 1930    5   -1  -12   10  208    7  179  205   57   -4  -35   -8
 1931   -6   17  -15   42   51   21  206 -673  187 -171   38   -2
 1932   10   13   18  -16  114  -22   26  312  -21  -62  -11  -11
 1933    7    4    3    8  152  404  262  306 -126 -151  105    7
 1934   -5  -10    9  -15 -166   12 -111  215 -109  -58  -29  -12
 1935   11   -5   -2  -23  -75  111  132  624   15  -58  -11  -11
 1936   -6    3  -16   45  160  118  170  603  103  -59   73   -1
 1937   -6   -7   -2  -34  -64 -141  -69  106 -201  -26   -7   -9
 1938   -5   -9   49  -38  -34 -117   44  119   42   47   -6  -12
 1939   -5    4    9  -52   96  -44  -42  269  121   40  -16   -3
 1940    1  -10   -3  -30  -58    3 -298  220 -160  141  -21  -11
 1941   -1  -10   -5  -19   47   -3 -179 -477  -65 -252    5  -10
 1942   -2    7  -11   11   29 -206 -253   97 -503  -51   23    0
 1943   -1    0    6  -29    6  -30 -160  478  308   12  -12   71
 1944   -6   -9    2   -1 -173  -60 -333 -111  -14   85    3   -5
 1945   -6  -10  -23  -22  -53 -205   53  566   50  -26  -27  -13
 1946    6  -10  -11  -39  -63 -100   68  192  133   98  -29  -10
 1947   -4   -2  -29  -63 -168  -84 -227  262   33 -192    0   -6
 1948   -5    6  -19  120  -29  276  -97   30 -350 -144  -30  -12
 1949    0   -9    7   -4 -107 -101  -61  146 -456 -141   -6   36
 1950    3    0  -28  -48  -58 -106  154  930  321   94  -26  -10
 1951    1    3   34  -22   86  -94 -195   32  241  711   76   -8
 1952   -4   -8  -21  -53   71  -81  188   86  814   68  -23   -5
 1953   -3   15   11  -31  224  276  338  -91   41   15   16   20
 1954   -5   61    8   54   56  102  390  661 -188  -65  125   -9
 1955    0   -4   49   33  -26  174  469   10  237   16  -22   26
 1956    0    9   25    2  -86  -55   61  113  182  -68  -16   69
 1957    1   -6   -1    4  162  140   71  109  261  296   17    0
 1958   10   -2   -6   29  -59  156  167  800  -82  -81  129   -5
 1959   -2   -5  -13  -32   92 -113 -270  518   62 -238    8  -13
 1960   -6  -11   -5    4  -10   62  190 -201  124 -152   -8    1
 1961   -2  -11  -13  -15  -90   80  219   54  -57 -260  -13   -7
 1962   -6  -10  -16   52   -3   74  -37  411 -125   41   80  -14
 1963   -2    9  -19   43  -41  -59  -56   52 -178  396  -32  -14
 1964   -2  -11    4  -20   42  163  177  342   38 -208  -32   51
 1965   30    5  -29  -58  -64  176 -211  249  195  -83  -21  -14
 1966   -6  -11    7   21    7  111 -506 -267  330  381  -28   -7
 1967   -6    1   11   11  -85   -8   -9  226  262   38  -18   -9
 1968   -6   52   38  175   22    9 -101 -610 -212 -125   -6    5
 1969   -4   -8   14  -25  -71  -61  209   41  -10  297   -4  -13
 1970   -6  -11  -13  -45   32 -235  -14 -133 -120 -273  -25  -13
 1971   -6    2   18    5 -104 -200 -176   28 -230 -264  -31    8
 1972    2   -4  -12   25   47  -22 -499 -669 -505  -94  -25    0
 1973   -6   -9  -19  -21  -61 -133 -209 -413 -467 -235  -32   -8
 1974   -6  -12   -4  -45  -99 -197   31   -4 -167 -149  -25  -13
 1975   -6  -10   -7  -32   13 -160  405 -266  -25 -186  -34  -10
 1976   11    6  -10   -1   34    6 -325 -480 -210  384   17    9
 1977    4  -11  -17  -75  -51 -160 -399 -544 -152 -209  -50   -9
 1978   -3   -7   21  123   10  -56  142 -483  -72   48   -3   -3
 1979   28  -12   -6  -59   13  208 -204 -503 -307  -97    6   -4
 1980   -1   14  -35  -42  -13  -93 -211 -264 -363 -195  -10   -6
 1981   -3   -4   10   27   76  -38   11 -400 -383 -207  -42  -13
 1982   -6    4   14   39  -54 -157 -377 -367 -567  -58  -41  -12
 1983   -6   -4  -20  -60  -87  -51 -470 -767 -511 -310  -41  -13
 1984   -6  -11   -2   -9   52 -109 -484-1058 -377 -177   -2  -13
 1985   -3  -10    5  -51 -151 -103  -66 -327 -326 -249  -40   -6
 1986   -6   -6  -23  -32  -39 -211 -283 -657   43 -164  -32  -14
 1987   -6  -10  -12  -92 -122  -66 -408 -550 -321 -102  -50  -13
 1988   -3   -5  -23   23 -136  -52 -168  184  -55 -246  -19  -13
 1989   -6   -6    6  -53 -129   -8 -167   21 -389  -51  -30    2
 1990    1  -12  -35  -24  -19 -185 -148 -541 -489 -192  -32   -9
 1991   -4    3   19    1  141  -81  -53 -270 -615   33  -49  -12
 1992   29   17  -29  -28   36  -98  -98 -351 -436 -196  -14  -13
 1993   -5   -7    0  -41 -130 -124  -50 -369 -335 -190  -17  -13
 1994   -5   -5  -15  -26  -59 -113 -162   78  201  234   -7  -14
 1995   -5  -10    4   25  -30 -103 -277 -174 -172 -176  -23   59
 1996   -3   -2  -20  -15   21  -45 -225 -294 -139  -68  -24   -4
 1997   -3  -10    9   15   63  129 -526 -468 -178  -87  -26  -13
 1998    0   -6  -27   11    2 -148 -360 -143  319 -158  -34  -11
 1999   -3   -9    0  -20  -46 -240  112  435 -131  310  -17  -13
 2000   10   -9  -11  -34  -79  -45 -133 -315 -394   12  -11  -12
 2001   -5  -11  -22   55    5   51  -52 -384 -284 -194   -1  -12
 2002   35  -12  -12  -28 -102 -226 -358 -613 -328   84  -35   -2
 2003   -2    7    7   11  -50   90   28  -85  -23   19   -2  -13
 2004   84   19   -8   28  -41  -64  153 -284 -439 -303    1   -6
 2005    5   24   10  -17  -39  215  -33 -305 -161 -184  -26  -13
 2006  -10    5  -15  -46  -51  -69 -308 -295   36  -67  -39  -13
 2007   -8   -9  -23   46 -119 -236 -191   65 -288 -250   76  -12
 2008   -7    7   -7  -51   -1  103   51   -3 -277  -18  -34   -5
 2009   -5    0    7  -47  -63  -79 -220  -47  143  -99    0  -11
 2010   -6  -14  -23  -21   -8   50   56  -94  490   49  -33  -14
 2011   -6   -2   -8  -23  -75  -32 -320   51 -288 -163  -38  -12
 2012   -6   -1   -6   -2   22  -82   59  186  169  -92    9  -12
 2013   -1  -14   -5   92  -72 -182 -392  278 -134  -42  -30   -6
 2014    7   -8  -13   14   94 -196 -370 -196 -149  -40  -20   -9
 2015   -9    1  -14  -82 -150                                   


JJASO-means in 0.1 mm/month with respect to 1900-2013, so "-82" is
-0.82 cm/month.

        +0    1    2    3    4    5    6    7    8    9
 1900  -82   91 -214  -33  -60  213  348 -136   51  204
 1910   32 -137  -15 -260   -2  -84   46  -18  234  -74
 1920   64  -88  144   45  194   67  -68  274  121  171
 1930  139  -35   97  189   40  215  237  -16   77  119
 1940   32 -145 -133  172  -36  138  129    9   -7  -72
 1950  329  189  266  167  231  232   97  226  243   42
 1960   55   58  123   82  153  115   60  152 -157  146
 1970 -104 -118 -307 -241  -46    4  -75 -242  -34 -130
 1980 -175 -153 -255 -371 -391 -164 -204 -239  -17  -68
 1990 -261 -147 -185 -163   98 -130 -104 -176  -47  147
 2000 -125 -122 -238   56 -137  -43  -90 -129   22  -10
 2010  161 -100   98  -35

Same data as a 2-column table (year, value in cm/month).

November 2013

Todd Mitchell ( mitchell@atmos.washington.edu )

JISAO data